JP2008155230A - Method for designing casting plan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for designing a casting plan by which the quality of a casting can be guaranteed even if casting conditions are varied. <P>SOLUTION: The method for designing the casting plan based on the heat-transfer solidification analysis using an analysis model formed from a plurality of elements comprises: a stage (S300) where casting conditions for a casting on a plurality of standards are set to the analysis model; a stage (S310) where, to the casting conditions of the casting on the above plurality of standards, the heat physical property values corresponding to the respective casting conditions for the casting on the above plurality of standards are calculated; a stage (S320) where, using the above calculated heat physical property values, the heat-transfer solidification analysis for the above casting respectively corresponding to the casting conditions on the above plurality of standards is practiced; and a stage (S340) where it is determined whether or not the information obtained from the heat-transfer solidification analysis respectively corresponding to the casting standards on the above plurality of standards lies within a prescribed quality allowable range. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a casting plan design method, and more particularly to a casting plan design method using simulation by an electronic computer.

  In order to produce a sound and inexpensive casting, it is necessary to examine the shape of the casting and the design policy of the casting in advance. As one means for that purpose, casting analysis using an electronic computer (hereinafter referred to as “computer”) is widely used.

  There are various types of casting analysis, such as flow analysis, deformation analysis, and heat transfer solidification analysis. In particular, heat transfer solidification analysis predicts mechanical properties of castings (for example, hardness and strength of castings) and shrinkage nests. It is an important analysis method for predicting casting defects due to defective metal structures (for example, Patent Document 1 and Patent Document 2).

  In general heat transfer solidification analysis, analysis models (models configured by dividing a casting or mold region to be analyzed into a plurality of elements (hereinafter referred to as "cells")) are adjacent to each other. In this analysis method, the heat flux in a minute time is calculated, and this is sequentially repeated at every minute time interval to obtain the temperature change of the analysis model.

  The calculation of the heat flux between the cells is performed using thermophysical values set for each cell, for example, solidification start temperature, solidification latent heat amount, specific heat, thermal conductivity, and the like.

  By the way, when casting conditions fluctuate in daily operations, it is conceivable that the thermophysical property value of the casting fluctuates accordingly. Variations in thermophysical values directly affect the solidification morphology of the casting and can therefore have a significant impact on the quality of the casting.

However, in the conventional heat transfer solidification analysis method, only one level value is used as the thermophysical property value of the casting for each type of metal material of the casting, regardless of the fluctuation of the casting conditions, and the analysis result of the target casting The heat transfer coagulation analysis was repeatedly performed by changing the shape of the analysis model until the quality was satisfied.
Japanese Patent Laid-Open No. 7-113771 JP-A-8-313464

  Therefore, in the above conventional heat transfer solidification analysis method, the quality of the casting with respect to the thermophysical property value of the one-level casting used for the analysis is guaranteed regardless of the fluctuation of the casting condition, and the fluctuation of the casting condition is not guaranteed. There is a problem that it is impossible to guarantee the quality of the casting against the thermophysical property value which changes with the above.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a casting method design method capable of guaranteeing the quality of a casting even when casting conditions fluctuate.

  In order to achieve the above object, a casting plan design method according to the present invention is a casting plan design method based on heat transfer solidification analysis of a casting using an analysis model formed from a plurality of elements, A step of setting casting conditions for a plurality of levels of castings, a step of calculating thermophysical values of the castings corresponding to the casting conditions of the castings of the plurality of levels, and using the calculated thermophysical values, Performing heat transfer solidification analysis of the casting corresponding to each level of casting conditions, and information obtained from the heat transfer solidification analysis corresponding to each of the plurality of levels of casting conditions is within a predetermined acceptable quality range. Determining whether or not.

  Further, in order to achieve the above object, a casting plan design apparatus for a casting according to the present invention is a casting plan design apparatus based on a heat transfer solidification calculation of a casting using an analysis model formed from a plurality of elements, Casting condition setting means for setting casting conditions for a plurality of levels of castings for the analysis model, thermophysical property value calculating means for calculating thermophysical values of the castings corresponding to the casting conditions for the plurality of levels of castings, Heat transfer solidification analysis means for executing heat transfer solidification analysis of the casting corresponding to each of the plurality of levels of casting conditions using the calculated thermophysical property values, and heat transfer solidification analysis corresponding to the plurality of levels of casting conditions, respectively. Determining means for determining whether or not the information obtained from the above is within a predetermined acceptable quality range.

  In order to achieve the above object, a casting plan design program for a casting according to the present invention is a casting plan design program based on a heat transfer solidification calculation of a casting using an analysis model formed from a plurality of elements, Using a procedure for setting casting conditions for a plurality of levels of castings for the analysis model, a procedure for calculating thermophysical values of the castings corresponding to the casting conditions for the castings of multiple levels, and using the calculated thermophysical values The procedure for executing the heat transfer solidification analysis of the casting corresponding to each of the plurality of levels of casting conditions and the information obtained from the heat transfer solidification analysis corresponding to each of the plurality of levels of casting conditions include predetermined quality tolerances. And a procedure for determining whether or not it is within the range.

  According to the casting plan design method, the casting plan design device, and the casting plan design program of the casting according to the present invention configured as described above, the thermophysical property value of the casting corresponding to each of a plurality of levels of casting conditions is calculated. Conducts heat transfer solidification analysis. As a result, it is possible to guarantee the quality of the casting corresponding to the thermophysical property value of the casting which changes with the change of casting conditions, and to provide a highly accurate casting method design method.

  The inventor has focused on the fact that the change in the thermophysical property value of the casting can be read from the cooling curve indicating the temperature change when the molten metal in the casting solidifies. From this cooling curve, a relational expression between the casting conditions and the thermophysical property value of the casting is derived, and by applying this relational expression to the heat transfer solidification analysis, the casting quality corresponding to multiple levels of casting conditions is predicted. I found out that it would be possible.

  Hereinafter, a casting plan design method according to the present invention will be described in detail by dividing it into a first embodiment and a second embodiment with reference to the drawings. Note that the same reference numerals are assigned to the same components.

  First, a casting plan design apparatus for carrying out the casting plan design method according to the present invention will be described in detail.

  FIG. 1 is a block diagram showing a schematic configuration of a casting plan design apparatus for carrying out a casting plan design method according to the present invention. As shown in FIG. 1, a casting plan design apparatus (hereinafter referred to as “computer”) 100 according to the present embodiment includes a CPU 111, a RAM 113, a ROM 115, a hard disk 117, a display 121, and an input unit 131. Are connected to each other via a bus 141 for exchanging signals.

  The computer 100 is an electronic computer such as a personal computer, and executes heat transfer solidification analysis based on a heat transfer solidification analysis program (hereinafter referred to as “simulation program”) or processes information obtained from the analysis result. Or display it. The information obtained from the analysis result is, for example, the change in the cell temperature over time, the eutectic solidification start temperature, the solidification latent heat amount, the cooling rate, or the solidification time. Various information obtained from the analysis result (hereinafter referred to as these Information is referred to as “defect determination parameter”). Based on the defect determination parameters, the casting is compared and evaluated, for example, whether or not the product is an acceptable product (whether or not the quality of the casting is guaranteed) is determined.

  The CPU 111 executes various arithmetic processes necessary for the control of each part and the heat transfer solidification analysis based on the simulation program. The CPU 111 includes a casting condition setting unit (casting condition setting unit), a thermophysical value calculation unit (thermophysical value calculation unit), a heat transfer coagulation analysis unit (and heat transfer calculation unit and heat transfer coagulation analysis unit), and a determination unit (determination). And a cooling rate calculation unit (cooling rate calculation unit).

  The RAM 113 temporarily stores programs and data as a work area.

  The ROM 115 stores various programs and parameters for controlling basic operations of the computer 100 in advance.

  The hard disk 117 stores an OS (operating system) and programs and parameters for controlling predetermined operations of the computer 100. The hard disk 117 includes creation and modification of analysis models, calculation of various thermophysical values, processing or display of information obtained from analysis results, a program for executing comparison / evaluation of finished products based on defect determination parameters, etc. Programs necessary for general heat transfer solidification analysis are stored in advance. Furthermore, the hard disk 117 also functions as a storage area for storing analysis results. Note that the program necessary for the heat transfer coagulation analysis may be stored in advance in a recording medium (for example, a recording medium such as a CD-ROM or DVD-ROM). The computer 100 may execute the coagulation analysis.

  The display 121 is, for example, a CRT display or a liquid crystal display, and displays various types of information obtained from the analysis results.

  The input device 131 is a pointing device such as a mouse, a keyboard, or a touch panel, and receives input from a user.

  The casting plan design method according to the present invention is executed using the computer 100 configured as described above.

  The casting plan design method according to the first embodiment of the present invention will be described in detail below with reference to the drawings.

[First Embodiment]
FIGS. 2 to 9 are views for explaining a casting plan design method and a casting plan design apparatus according to the first embodiment of the present invention. FIG. 2 shows an example of a casting designed by the casting plan design method of the present embodiment, and FIG. 3 shows an operation flowchart of the casting plan design apparatus shown in FIG. This corresponds to the procedure of the casting plan design method according to the above. 4-9 is a figure used in order to demonstrate the processing content of the casting plan design method based on this Embodiment.

  With reference to FIG. 2, the casting designed by the casting plan design method of the present embodiment will be described. FIG. 2 shows a casting 200 and a chiller 210 designed by the casting plan design method of the present embodiment. As shown in FIG. 2A, the casting 200 is a cast iron component for a vehicle, and is a cam-shaped member including a base portion 200a and a nose portion 200b. As shown in FIG. 2B, the thickness of the base portion 200a of the casting 200 is designed to be thinner than the thickness of the nose portion 200b. Accordingly, the portion A of the base portion 200a is a portion that requires relatively low hardness because of the shaft hole machining, and the portion B of the nose portion 200b is a portion that requires relatively high hardness from wear resistance. In the present embodiment, the casting 200 and the chiller 210 are used as an analysis model.

  Further, in the present embodiment, as casting conditions, a fading time indicating the elapsed time from the time when the molten metal of the casting is discharged from the melting furnace to the pouring ladle is used, and casting is performed for two levels of fading time. A case where it is determined whether or not the casting 200 to be performed is included in a predetermined quality assurance range will be described as an example. Hereinafter, the casting plan design method according to the present embodiment will be described in detail.

As shown in FIG. 3, first, a plurality of levels of casting conditions are set for the analysis model (S300).
). Specifically, an analysis model formed from a plurality of elements of a casting to be analyzed is created, and a plurality of levels of casting conditions relating to casting are set for the analysis model.

  The analysis model is created by data necessary for creating the analysis model, for example, shape data (shape data necessary for solidification analysis of the casting, such as the shape of the casting to be analyzed, the design shape of the casting, the shape of the mold) , Various data necessary for general simulation, such as the number of element divisions, casting time, material forming the casting, the temperature of the molten metal of the casting, etc. are input to the computer 100 from the input device 131, and the various data input The processing is terminated when the computer 100 calculates based on the above. The analysis model is created as a mesh model. The initial conditions are set by inputting various data from the input device 131 to the computer 100. Note that data, initial conditions, casting conditions, and the like necessary for creating the analysis model may be stored in advance in the hard disk 117 or the like, or manually input by an operator. The number of element divisions is equal to the number of cells (number of elements) of the mesh model, and the element division is performed on the mesh model at the time of simulation. A cell refers to each element of the mesh model.

  The setting of the casting conditions includes at least one of the components of the material forming the casting, the molten metal temperature of the material forming the casting, the type of the inoculum, the added amount of the inoculum, or the fading time. Set as.

  In the present embodiment, as the casting conditions of a plurality of levels, the fading time is 0 minute (hereinafter referred to as “fading time 0 minute”) and the fading time is 15 minutes (hereinafter referred to as “fading time 15 minutes”). 2 levels of casting conditions are set. As already explained, the fading time means the elapsed time starting from the time when the molten metal of the casting is poured from the melting furnace into the pouring ladle. The longer this fading time is, the more graphitization of the molten metal of the casting occurs. The performance declines. Usually, since the maximum fading time in a production factory is 15 minutes, two levels of the fading time of 0 minutes and the fading time of 15 minutes are adopted as casting conditions.

  Next, one casting condition is selected from the set casting conditions of a plurality of levels (S310). Specifically, one casting condition is selected from among the casting conditions of fading time 0 minutes and fading time 15 minutes, for example, fading time 0 minutes is selected.

  Next, a thermophysical value corresponding to the casting condition of the selected casting is calculated (S320). As described above, the thermophysical property value is calculated by using a relational expression (for example, a conversion table for calculating a thermophysical property value corresponding to the casting condition) between the casting condition stored in the hard disk 117 in advance and the thermophysical property value of the casting. Used to calculate the thermophysical property value of the casting corresponding to the selected casting condition. In the present embodiment, the thermophysical property value corresponding to the fading time of 0 minutes, which is the casting condition selected in step S310, is calculated.

  Below, the calculation method of the thermophysical value corresponding to casting conditions is demonstrated in detail. In this embodiment, since fading time is adopted as casting conditions, the relationship between fading time and eutectic solidification start temperature, which is one of thermophysical values, will be described as an example.

FIG. 4 shows the change in the cooling curve of the casting with the fading time. The horizontal axis represents time, and the vertical axis represents temperature. The cooling curve A ₀ is a cooling curve with a fading time of 0 minutes, and the eutectic solidification start temperature at this time is T ₀ . Cooling curve A ₁₅ is a cooling curve of the fading time of 15 minutes, the eutectic solidification starting temperature at this time is T _15. As shown in FIG. 4, the eutectic solidification start temperature decreases as the fading time increases. This indicates that when the casting condition is changed, the thermophysical property value corresponding to the cooling curve also changes because the cooling curve changes with the change of the casting condition.

  Then, by processing these cooling curves in numerical values, a relational expression between the fading time and the eutectic solidification start temperature can be derived. Other thermophysical values can be derived in the same manner.

  Next, heat transfer solidification analysis is performed using the thermophysical property values calculated in the process of step S320 (S330). The basic principle of heat transfer solidification analysis is to set the thermophysical property values according to the characteristics of the cell in the analysis model (model configured by dividing the casting or mold area to be analyzed into multiple cells) Calculate the heat flux at minute time intervals between adjacent cells. Then, the heat flux calculation is repeated for each minute time interval to obtain the temperature change of the analytical model.

  The calculation of the heat flux is executed using a general heat transfer calculation method. Here, the setting according to the characteristics of the cell means that a predetermined thermophysical property value is set for a cell belonging to a casting (for example, the casting 200 shown in FIG. 2), and other cells, that is, a mold region ( For example, for cells belonging to the chiller 300) shown in FIG. 2, it means that the thermophysical value of the material to which each belongs is set. The thermophysical property values are physical property values necessary for heat transfer calculation such as solidification start temperature, liquidus temperature, specific heat, and thermal conductivity.

  At the start of analysis, a predetermined initial temperature is given to all the cells, but the initial temperature changes after a minute time interval by heat transfer calculation. At the start of analysis, the temperature of the cell belonging to the casting is set higher than the temperature of the cell belonging to the mold region. For this reason, the temperature of the cell which belongs to a casting as a result of heat transfer calculation naturally falls.

  In the present embodiment, the temperature change data obtained from the analysis result is digitized and processed, and the cooling rate for each cell is calculated. The cooling rate is calculated as follows.

Assuming that the temperature of the cell just before the Δt time which is a minute time interval from when the cell reaches the eutectic solidification start temperature _TL is T, the cooling rate 'dT / dt' is expressed by the following equation (1). I can express.

  Thus, the reason for calculating the cooling rate is that the cooling rate is an important factor that affects the mechanical properties of the casting, which is an indicator of the quality of the casting, for example, the hardness of the casting (cooling rate and hardness of the casting). A detailed description of the relationship will be given later).

  Next, it is determined whether or not heat transfer solidification analysis has been executed for all casting conditions (S340). When the heat transfer solidification analysis is not executed for all casting conditions (S340: NO), other casting conditions are selected (S370), and the processing from step S320 onward is executed again based on the other casting conditions. . Specifically, the fading time of 15 minutes is selected, and the processes after step S310 are executed again.

  And when heat transfer solidification analysis is performed with respect to all the casting conditions (S340: YES), is the information obtained from the heat transfer solidification analysis corresponding to the said casting conditions within a predetermined quality tolerance range? It is determined whether or not (S350). Specifically, the hardness of the casting is calculated based on the cooling rate for each cell calculated in the process of step S330, and the calculated hardness is within a predetermined quality tolerance (hereinafter referred to as “standard value”). It is determined whether or not there is. Below, the relationship between a cooling rate and the hardness of a casting and the processing content of step S350 are demonstrated in detail.

  FIG. 5 shows the relationship between the cooling rate and the hardness of the casting. The horizontal axis represents the distance from the part C of the casting 200 shown in FIG. 2, and the vertical axis represents the hardness of the casting 200 shown in FIG.

  As shown in FIG. 5, the cooling rate and the hardness of the casting have a substantially proportional relationship.

The standard value is, for example, the standard value of hardness at a position at a distance L _A from site C A (see FIG. 2 (A)) is less than H _A, site in the distance L _B from site C B (FIG. 2 standard value of hardness (a) reference) determined to be equal to or greater than H _B. As already described, the part A is a part that requires a relatively low hardness, and the part B is a part that requires a relatively high altitude.

In this case, it can be seen from the relationship shown in FIG. 5 that the cooling rate of the part A is _VA or less, and the cooling rate of the part B is required to be V _B or more as a standard value. Since the cooling rate is a factor that affects the hardness of the casting, in the present embodiment, the standard value is determined from the relationship between the cooling rate and the hardness of the casting.

FIG. 6 shows the relationship between the distance from the tip of the casting (site C in FIG. 2) and the cooling rate. The horizontal axis represents the distance from the part C shown in FIG. 2, and the vertical axis represents the cooling rate. A curve C ₀ shows a case where the fading time is 0 minute, and a curve C ₁₅ shows the case where the fading time is 15 minutes. As described above, the following cooling speed V _A of site A, but more than V _B cooling rate of site B is is required as standard value, as shown in FIG. 6, when the fading time of 0 minutes, the site While the cooling rate of _A satisfies the standard value of the cooling rate V _A or less, the cooling rate of the part B does not satisfy the standard value of the cooling rate V _B or more.

When the fading time is 15 minutes, the cooling rate of the part B satisfies the standard value equal to or higher than the cooling rate V _B, while the cooling rate of the part A does not satisfy the standard value equal to or lower than the cooling rate _VA . In the process of step S350, in this way, it is determined whether the value is within the standard value from the relationship between the cooling rate and the hardness of the casting.

  Again, it returns to description of the processing content of step S350. As described above, when at least one analysis result is not within the standard value (S350: NO), the analysis model is changed (S360). For example, as shown in FIG. 7, the analysis model is changed so that the thickness of the base portion 200 a of the cast iron component 200 is increased and the capacity of the bottom portion of the chiller 210 is increased. The analysis model can be changed manually by the user, or the analysis model stored in advance in the hard disk 117 can be automatically read and changed. In FIG. 7, the same components as those in FIG. 2 are denoted by the same reference numerals. Then, the processing after step S310 is repeated using the changed analysis model.

  And when it determines with the result obtained from the heat-transfer solidification analysis corresponding to all the casting conditions being within a specification value, a process is complete | finished (S350: YES). Specifically, the following processing is executed.

FIG. 8 shows the relationship between the distance from the tip of the casting after the change of the analysis model (part C in FIG. 7) and the cooling rate. The horizontal axis represents the distance from the part C shown in FIG. 7, and the vertical axis represents the cooling rate. A curve C ′ ₀ shows a case where the fading time is 0 minute, and a curve C ′ ₁₅ shows a case where the fading time is 15 minutes.

As shown in FIG. 8, when the fading time is 0 minute, the cooling rate of the part A satisfies the standard value of the cooling rate V _A or less, and the cooling rate of the part B satisfies the standard value of the cooling rate V _B or more. .

In addition, when the fading time is 15 minutes indicated by the broken line in FIG. 7, the cooling rate of the part B satisfies the standard value of the cooling rate V _B or more, and the cooling rate of the part A satisfies the standard value of the cooling rate _VA or less. ing.

  In this way, the shape of the analysis model is changed until the standard value is satisfied, and the processing is terminated if the analysis results for the two levels of the casting condition fading time 0 minutes and fading time 15 minutes satisfy the standard values.

  According to the casting plan design method and the plan design apparatus for a casting according to the present invention configured as described above, thermophysical values corresponding to a plurality of levels of casting conditions are calculated, and the calculated thermophysical values are used. A heat transfer solidification analysis is performed. Then, the quality of the casting is determined based on the analysis result, the analysis model is changed until it is determined that the quality of the casting is within a predetermined standard value, and the heat transfer solidification analysis is repeatedly executed. As a result, it is possible to guarantee the quality of the casting corresponding to the thermophysical property value of the casting that changes with the change in casting conditions, and to provide a highly accurate casting method design method.

[Second Embodiment]
In the first embodiment, it has been explained that an analysis result with higher accuracy than that of the conventional method can be obtained by considering that the thermophysical property value of a casting changes depending on casting conditions. The casting conditions are mainly factors until the molten metal is poured into the mold, but there are also factors that affect the thermophysical property value of the casting after being poured into the mold. After pouring into the mold, a factor that affects the thermophysical property value of the casting is the cooling rate of the casting melt. Therefore, in the present embodiment, a case will be described in which the thermophysical property value of the casting changes in accordance with the cooling rate of the molten metal in addition to the change of the thermophysical property value in accordance with the casting conditions.

  9 to 12 are diagrams for explaining the heat transfer solidification analysis method for a casting according to the embodiment of the present invention. 9 and 10 show an operation flowchart of the casting plan design apparatus shown in FIG. 1, and this flowchart corresponds to the procedure of the casting plan design method according to the present embodiment. FIG. 11 to FIG. 12 are diagrams used for explaining a thermophysical property calculation method in the casting method design method according to the present embodiment. In the present embodiment, the processing is performed under the same casting conditions as in the first embodiment. Accordingly, the same processing contents as those in the first embodiment will not be described in detail in order to avoid redundant description.

  As shown in FIG. 9, first, a plurality of levels of casting conditions are set for the analysis model (S400).

  Next, one casting condition is selected from the set casting conditions of a plurality of levels (S410).

  Next, a thermophysical value corresponding to the selected casting condition is calculated (S420). The thermophysical property value calculated in the processing of step 420 is a thermophysical property value calculated in the same manner as the processing of step S320 in FIG. 3, but this is a thermophysical property value considering only the fading time that is a casting condition. Therefore, in the present embodiment, it means a thermophysical value before solidification of a cast molten metal (hereinafter referred to as “thermophysical value before solidification”).

  Next, heat transfer coagulation analysis processing is executed using the thermophysical property values calculated in step S420 (S430). Here, the processing content of step S430 will be described in detail.

  FIG. 10 is a flowchart showing the processing contents of the subroutine of step S430.

  As shown in FIG. 10, first, the thermophysical property before solidification calculated in the process of step S420 is set for the analysis model, and the heat transfer calculation between cells adjacent to each other is executed (S431). The thermophysical property value before solidification is set according to the characteristics of the cell, and the heat transfer calculation is executed.

  Next, based on the result of the heat transfer calculation, it is determined whether or not the cell temperature has reached a predetermined temperature (hereinafter referred to as “cooling rate calculation temperature”) (S432). If the cell does not reach the cooling rate calculation temperature, the processing from step S431 is repeated (S432: NO). If the cell temperature reaches the cooling rate calculation temperature (S432: YES), the process proceeds to step S433. In the process of step S432, it is determined whether or not the cooling rate calculation temperature has been reached for each cell.

  Next, for the cell that has reached the cooling rate calculation temperature, the cooling rate of the cell is calculated (S433). Below, the calculation method of the cooling rate in step S433 is demonstrated in detail.

The cell temperature at the time when the cell temperature reaches the predetermined temperature is T _n , and the temperature of the cell before the time “Δt” that is a minute time interval from the time when the cell reaches the predetermined temperature is T _n−. Assuming ₁ , the cooling rate 'dT / dt' is expressed by the following equation (2).

  The cooling rate calculation temperature can be set to an arbitrary temperature, but the set temperature is preferably equal to or higher than the eutectic solidification start temperature in actual casting. However, in the analysis at present, the eutectic solidification start temperature in actual casting is unknown. Therefore, the cooling rate calculation temperature is preferably the eutectic solidification start temperature when the molten casting is solidified over an infinite amount of time, particularly when the material forming the casting is cast iron. It is preferable to set the eutectic solidification start temperature when the carbon in the molten metal is completely graphitized. This is because if such a temperature is set, the cooling rate calculation temperature in any cell of the analysis model can be prevented from being lower than the eutectic solidification start temperature in actual casting.

  Next, based on the calculated cooling rate, the thermophysical value at the time of solidification when eutectic solidification of the molten metal of the casting is started (hereinafter referred to as “thermophysical value at the time of solidification”) and the molten metal of the casting A thermophysical value after solidification after eutectic solidification is completed (hereinafter referred to as “thermophysical value after solidification”) is calculated (S434). The thermophysical value at the time of solidification and the thermophysical value after the solidification are calculated for each cell by using the cooling rate obtained from the process of step S433.

  Below, the thermophysical value at the time of solidification and the calculation method of the thermophysical value after the solidification will be described in detail. A method for calculating the eutectic solidification start temperature and the solidification latent heat amount will be described as an example of thermophysical property values during solidification.

The eutectic solidification start temperature _TL and the solidification latent heat quantity q, which are one of the thermophysical values at the time of solidification, can be expressed by the following equations as a function of the cooling rate 'dT / dt'.

Here, _TLmax is the eutectic solidification start temperature when the carbon element in the casting melt is completely graphitized.

  Below, the calculation method of Formula (3) and (4) used by this Embodiment is demonstrated in detail.

  FIG. 11 is a schematic diagram of a cooling curve when a casting is cast while artificially changing the cooling rate. The horizontal axis represents time, and the vertical axis represents the temperature of the casting. This cooling curve shows the result of actual measurement by repeatedly casting the casting. The reason why the measurement is performed while changing the cooling rate in this manner is that, as already described, if the casting conditions are changed, the cooling curve also changes, and as a result, the corresponding thermophysical property value also changes.

Cooling curve B ₁ represents a cooling curve when the carbon element was gradually cooled casting has completely graphitized, eutectic solidification starting temperature at this time is T _3. Eutectic solidification starting temperature _{T 3} is equal to _{T Lmax.} Cooling curve A ₂ is a cooling curve when not change the artificially cooling rate, the eutectic solidification starting temperature at this time is T _2. Cooling curve A ₃ is the cooling curve of when fully ledeburitic of quenched casting, eutectic solidification starting temperature at this time is T _1. As shown, the cooling curve B ₂ is present in a region surrounded by the cooling curve B ₁ ~B _3. At this time, the eutectic solidification starting temperature T ₅ is present in the range of the eutectic solidification starting temperature T ₄ through T _6.

FIG. 12 shows the result of determining the relationship between the eutectic solidification start temperature and the cooling rate at the start of eutectic solidification from the measurement results of the cooling curves B _{1 to} B ₃ shown in FIG. The horizontal axis represents the cooling rate at the start of eutectic solidification, and the vertical axis represents the eutectic solidification start temperature.

As shown in FIG. 12, the eutectic solidification start temperature decreases in inverse proportion to the cooling rate at the start of eutectic solidification (see curves B ′ _{1 to} B ′ ₃ ). If the curve showing the relationship between cooling rate and eutectic solidification starting temperature of the casting of the casting in one casting conditions is B _'1, if by changing the casting conditions, the eutectic solidification starting temperature of the cooling rate and the casting of the casting For example, the curve B ′ ₂ or the curve B ′ ₃ changes. Specifically, for example, when the casting cooling rate is V _C , the eutectic solidification start temperature in the curve B ′ ₁ is T ₇ , so if the casting conditions are changed, the eutectic solidification start in the curve B ′ ₂ temperature it can be seen that the change in T _6. Further, in curve B ′ ₂ , it can be seen that when the casting cooling rate changes from V _C to V _D , the eutectic solidification start temperature changes from T ₆ to T ₇ .

  Each curve indicates an inflection point at a specific eutectic solidification start temperature and a specific cooling rate. This inflection point is called the chill critical cooling rate. When the cooling rate at the start of eutectic solidification is larger than the chill critical cooling rate, iron-cementite eutectic solidification occurs, which is higher than the chill critical cooling rate. It is known that iron-graphite eutectic solidification occurs when the cooling rate is low.

  Here, in the present embodiment, the cooling rate used for calculating the thermophysical value at the time of solidification and the thermophysical value after solidification is the eutectic solidification start of the actual melt as described in the process of step S433. The eutectic solidification start temperature when the casting melt is solidified over an infinite time rather than the temperature (when the material forming the casting is cast iron, the carbon in the casting melt is completely graphitized. Eutectic solidification start temperature). However, since the difference between the eutectic solidification start temperature of the molten metal in actual casting and the eutectic solidification start temperature when the carbon element in the molten metal of the casting is completely graphitized is in a practically negligible range, FIG. By formulating the curve shown, it can be expressed as Equation (3).

Similarly, Equation (4) is calculated from the measurement results of the cooling curves B _{1 to} B ₃ shown in FIG. Formula (4) is calculated by general iterative analysis (detailed explanation is omitted) using the amount of latent heat of solidification as a variable.

  By the way, although the thermophysical value after solidification can be calculated from the cooling rate as described above, the thermophysical value calculated directly from the cooling rate is not used, but the solidified structure (for example, area ratio of pearlite / ferrite) It is preferable to use thermophysical values calculated from the relationship with

  Thus, the reason for using the thermophysical value calculated | required from the relationship with a solidification structure | tissue is not used as it is, but the thermophysical value after the solidification computed from a cooling rate is as follows.

  The cast metal has a different metal structure after solidification depending on the cooling rate. For example, ductile is known to produce chill when rapidly cooled, and to crystallize ferrite when slowly cooled. Thus, since the metal structure after solidification differs between when the casting is rapidly cooled and when it is gradually cooled, the thermophysical values after solidification are different.

  Therefore, it is preferable to calculate the thermophysical value after solidification from the relationship between the cooling rate and the solidified structure as described above, rather than using the value calculated from the cooling rate as it is as the thermophysical value after solidification. As a result, a highly accurate analysis result in consideration of the solidified structure can be obtained.

  When the material forming the casting is cast iron and the cooling rate is higher than a predetermined rate, the thermophysical value during solidification and the thermophysical value after solidification are determined based on the cooling rate in iron-cementite eutectic solidification. When the calculated cooling rate is equal to or lower than the predetermined rate, it is preferable to calculate the thermophysical value during solidification and the thermophysical value after solidification based on the cooling rate in iron-graphite eutectic solidification. .

  Thus, the reason for calculating the thermophysical value based on the predetermined cooling rate is that the relational expression between the cooling rate and the thermophysical value at the time of solidification and after solidification changes with the chill critical cooling rate in between. is there.

  Therefore, when the chill critical cooling rate is set as a predetermined rate and the cooling rate is larger than the chill critical cooling rate, the heat during solidification and after solidification is calculated using the relational expression with the cooling rate in iron-cementite eutectic solidification. When the physical property value is calculated and the cooling rate is equal to or less than the chill critical cooling rate, it is preferable to calculate the thermophysical value at the time of solidification and after solidification using a relational expression with the cooling rate in the iron-graphite eutectic solidification. .

  Next, it is determined whether or not the cell has reached the eutectic solidification start temperature calculated in the process of step S434 (S435). When the temperature of the cell does not reach the calculated eutectic solidification start temperature, the processing after step S434 is repeated (S435: NO), and when the temperature of the cell reaches the calculated eutectic solidification start temperature (S435). : YES), the process proceeds to step S436.

  Next, for the cell that has reached the eutectic solidification start temperature, the thermophysical value at the time of solidification is set and the heat transfer solidification analysis is executed (S436).

  Here, when the material forming the casting is cast iron, it is preferable to use the eutectic solidification start temperature and the latent heat of solidification as the thermophysical values during solidification. In the case of castings, iron-cementite eutectic solidification tends to occur when the cooling rate is high, and iron-graphite eutectic solidification tends to occur when the cooling rate is low. This is because iron-cementite eutectic solidification and iron-graphite eutectic solidification have a remarkable difference in eutectic solidification start temperature and solidification latent heat amount among thermophysical values. In this way, by adding the eutectic solidification start temperature and the solidification latent heat amount among the thermophysical values at the time of solidification, the analysis accuracy is further improved.

  Next, based on the result of the heat transfer solidification analysis, it is determined whether or not the cell has completed solidification (S437). When the solidification of the cell is not completed, the processes after step S436 are repeated (S437: NO), and when the solidification of the cell is completed, the process proceeds to the process of step S438 (S437: YES).

  Next, the thermophysical value after the solidification is set for the cell that has been solidified, and a heat transfer solidification analysis is performed (S438). Then, when the solidification of all the cells is completed, the process is terminated, and the process proceeds to step S440 (see FIG. 9).

  Next, it is determined whether or not heat transfer solidification analysis has been executed for all casting conditions (S440). When the heat transfer solidification analysis is not executed for all casting conditions (S440: NO), other casting conditions are selected (S470), and the processes in and after step S410 are repeated. And when heat transfer solidification analysis is performed with respect to all the casting conditions (S440: YES), it progresses to the process of step S450.

  Next, it is determined whether or not the information obtained from the heat transfer solidification analysis corresponding to each casting condition is within the standard value (S450). When it is determined that at least one analysis result of the casting conditions is not within the standard value (S450: NO), the analysis model is changed (S460). And when it determines with the result obtained from the heat-transfer solidification analysis corresponding to all the casting conditions being within a specification value (S450: YES), a process is complete | finished.

  According to the casting method design method and the design apparatus according to the present invention configured as described above, thermophysical values corresponding to a plurality of levels of casting conditions are calculated, and further, thermophysical properties calculated from the cooling rate of the casting A heat transfer solidification analysis is performed using the values. As a result, an analysis result corresponding to the thermophysical property value of the casting that changes as the casting conditions change can be obtained, and a highly accurate casting method can be provided.

  Further, in the casting method design method and the design apparatus according to the present invention, by processing information obtained from the heat transfer solidification analysis results, the defect determination parameters in all or part of the analysis model are numerical values, colors, graphs, or It can be displayed using graphics.

  Moreover, the casting plan design method according to the present invention can be programmed so as to be readable by a computer, and the programmed data can be recorded on a computer-readable recording medium.

  INDUSTRIAL APPLICABILITY The present invention is useful in the technical field related to a casting method based on a heat transfer solidification analysis of a casting or a heat transfer solidification analysis of a casting.

It is a block diagram which shows schematic structure of the casting plan design apparatus for implementing the casting plan design method which concerns on this invention. 1 illustrates a casting that is designed by a casting method design method according to the present invention.

It is an operation | movement flowchart of the casting plan design apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the change of the cooling curve of a casting by fading time. It is a figure which shows the relationship between a cooling rate and the hardness of a casting. It is a figure which shows the relationship between the distance from the front-end | tip part of a casting, and a cooling rate. It is a figure which shows the analysis model which changed the analysis model shown in FIG. It is a figure which shows the relationship between the distance from the front-end | tip part of a casting, and a cooling rate. It is an operation | movement flowchart of the casting plan design apparatus which concerns on 2nd Embodiment of this invention. It is an operation | movement flowchart of the casting plan design apparatus which concerns on 2nd Embodiment of this invention. It is a figure explaining the calculation method of the thermophysical property value in the casting plan design method which concerns on 2nd Embodiment of this invention. It is a figure explaining the calculation method of the thermophysical property value in the casting plan design method which concerns on 2nd Embodiment of this invention.

Explanation of symbols

100 casting plan design equipment,
111 CPU,
113 RAM,
115 ROM,
117 hard disk,
121 display,
131 input section,
200 casting 210 chiller A ₀ , A ₁₅ cooling curve,
B ₁ ~B ₃ cooling curve,
C ₀ , C ₁₅ , C ′ ₀ , C ′ ₁₅ Curve showing the relationship between the distance from the casting tip and the cooling rate,
B ′ ₁ -B ′ ₃ Change rate curve of cooling rate at the start of eutectic solidification T _0, T ₁₅ , T ₁ -T ₇ eutectic solidification start temperature,
V _{A to} V _D cooling rate.

Claims (15)

A casting design design method based on heat transfer solidification analysis of a casting using an analysis model formed from a plurality of elements,
Setting casting conditions for multiple levels of castings for the analytical model;
Calculating thermophysical property values of the castings respectively corresponding to casting conditions of the castings of the plurality of levels;
Performing the heat transfer solidification analysis of the casting respectively corresponding to the plurality of levels of casting conditions using the calculated thermophysical property values;
Determining whether the information obtained from the heat transfer solidification analysis corresponding to each of the plurality of levels of casting conditions is within a predetermined acceptable quality range;
A casting method design method characterized by comprising: After determining whether it falls within the predetermined quality tolerance range,
The method further includes a step of changing the analysis model when at least one piece of information obtained from the heat transfer solidification analysis corresponding to each of the plurality of levels of casting conditions is out of the acceptable quality range. Item 2. A casting design method according to Item 1. After the step of changing the analysis model,
The step of determining whether or not the predetermined analysis quality is within the predetermined allowable range from the step of calculating the thermophysical value of the casting according to claim 1 is performed on the changed analysis model. Item 3. A casting design method according to Item 2. Performing a heat transfer solidification analysis of the casting corresponding to each of the plurality of levels of casting conditions,
Performing a heat transfer calculation between the elements adjacent to each other using the thermophysical property values before solidification of the melt of the casting;
Calculating a cooling rate of the element based on the heat transfer calculation;
Based on the calculated cooling rate, a thermophysical value at the time of solidification when the molten metal of the casting starts eutectic solidification and a thermophysical value after solidification after the molten metal of the casting has completed eutectic solidification are calculated. Stages,
Performing a heat transfer solidification analysis using the thermophysical value at the time of solidification calculated from the cooling rate and the thermophysical value after the solidification;
The casting method design method according to claim 1, comprising: Calculating the cooling rate of the element based on the heat transfer calculation,
The casting method design method according to claim 4, wherein the casting method is performed when the temperature of the element reaches a predetermined temperature.   6. The casting plan design method according to claim 5, wherein the predetermined temperature is a eutectic solidification start temperature when the molten metal of the casting is solidified by equilibrium over a certain time.   5. The casting design method according to claim 4, wherein the thermophysical value at the time of solidification is a thermophysical value including a eutectic solidification start temperature of the casting and a solidification latent heat amount of the casting.   5. The casting plan design method according to claim 4, wherein the thermophysical property value after solidification is a thermophysical property value calculated from the relationship between the calculated cooling rate and the solidification structure of the casting. The step of performing the heat transfer solidification analysis using the thermophysical value at the time of solidification calculated from the cooling rate and the thermophysical property value after the solidification,
Setting a thermophysical value at the time of solidification for an element that has started eutectic solidification;
Setting a post-solidification thermophysical value for an element that has undergone eutectic solidification;
The casting method design method according to claim 4, comprising: The thermophysical property value at the time of solidification includes a eutectic solidification start temperature calculated from the cooling rate,
The step of setting the thermophysical value at the time of solidification for the element that has started eutectic solidification,
The casting design method according to claim 9, wherein a thermophysical value at the time of solidification is set for an element that has reached the eutectic solidification start temperature. The stage of setting the casting conditions for multiple levels of castings is:
Setting at least one of the components of the material forming the casting, the molten metal temperature of the material forming the casting, the type of inoculum, the amount of inoculum added, and the fading time as the casting condition The casting method design method according to claim 1. After determining whether the quality is within the predetermined acceptable range,
The casting method design method according to claim 1, further comprising processing and displaying information obtained by the heat transfer solidification analysis. A casting design design device based on heat transfer solidification calculation of a casting using an analysis model formed from a plurality of elements,
Casting condition setting means for setting casting conditions for a plurality of levels of castings for the analysis model;
Thermophysical property value calculating means for calculating the thermophysical property value of the casting corresponding to the casting conditions of the castings of the plurality of levels;
Using the calculated thermophysical property value, heat transfer solidification analysis means for executing heat transfer solidification analysis of the casting respectively corresponding to the plurality of levels of casting conditions;
Determination means for determining whether the information obtained from the heat transfer solidification analysis corresponding to each of the plurality of levels of casting conditions is within a predetermined quality tolerance range;
A casting plan design device characterized by comprising: A casting design design program based on heat transfer solidification calculation of a casting using an analysis model formed from a plurality of elements,
A procedure for setting casting conditions of a plurality of castings for the analysis model;
A procedure for calculating a thermophysical value of the casting corresponding to casting conditions of the castings of the plurality of levels;
Using the calculated thermophysical property value, a procedure for performing heat transfer solidification analysis of the casting respectively corresponding to the plurality of levels of casting conditions;
A procedure for determining whether or not the information obtained from the heat transfer solidification analysis corresponding to each of the plurality of levels of casting conditions is within a predetermined quality tolerance range;
Casting program design program characterized by causing a computer to execute.   The computer-readable recording medium which recorded the casting plan design program of Claim 14.

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